While some individuals who become infected with herpesviruses are asymptomatic, others have moderate or severe symptoms. One factor that might explain differences in symptoms could be sequence differences (polymorphisms) in cellular proteins. We are determining if polymorphisms in cellular proteins correlate with infectivity of herpesviruses or severity of herpesvirus disease. [unreadable] [unreadable] We are trying to identify novel or known viruses as causes of diseases of uncertain etiology. Blood and tissues from patients are being examined by sensitive PCR tests in an attempt to find new or known viruses that are responsible for the diseases. Previously, we used these procedures to identify human herpesvirus 6 in lymph node biopsies from three patients who presented with fever and enlarged lymph nodes.[unreadable] [unreadable] Cytomegalovirus causes congenital disease which can result in deafness and mental retardation in neonates, and can cause severe viral pneumonia and colitis in transplant recipients and sight-threatening retinitis in patients with AIDS. Epstein-Barr virus (EBV) causes infectious mononucleosis and is associated with a number of malignancies including Burkitt lymphoma, nasopharyngeal carcinoma, Hodgkins disease, and post-transplant lymphoproliferative disease. Human CMV and EBV infect humans, but not small animals or nonhuman primates. The best models currently available for CMV and EBV are rhesus monkey CMV and EBV. The goal of this study is to develop an effective vaccine for these rhesus viruses and to use these as a model for vaccines for their human counterparts. We are using various approaches including soluble recombinant proteins and recombinant virus vectors expressing viral proteins.[unreadable] [unreadable] Herpesviruses result in lifelong infection in hosts. Vaccines are not available for herpes simplex virus, cytomegalovirus, or Epstein-Barr virus, all of which can reactivate when persons are immunosuppressed. Cellular immunity, especially virus-specific lymphocytes (CD8 T cells) are thought to be important to prevent the virus from reactivating. In addition, the amount of virus in latently infected cells and the number of latently infected cells has been postulated to be important in predicting the frequency of virus reactivation. Current techniques for measuring the number of latently infected cells and the number of copies of viral DNA in latently infected cells are very labor intensive and require expensive equipment. [unreadable] [unreadable] We have developed a new method to quantify the number of copies of viral DNA in latently infected cells and the number of latently infected cells in an animal model of herpes simplex virus infection. We infected mice with herpes simplex type 2 and one month later, when the virus had established a latent infection, we removed the latently infected trigeminal ganglia, treated the tissue with collagenase to disperse it into a single cell suspension, and plated the cells into 96-well plates. We then performed real-time PCR on each well of the plate and calculated the number of herpes simplex virus copies in each well. By assuming that the cells were distributed equally in the wells and that each well contained one or no virus-infected cells and using a mathematical formula (Poisson distribution) we were able to estimate both the number infected cells and the number of virus copies per infected cell.[unreadable] [unreadable] We validated this model by comparing the results using the model with calculations using a more exact method. The results using the model correlated very well with the more conventional technique. Since the frequency of virus reactivation is a likely a function of the amount of virus in latently infected cells and the number of latently infected cells, this new model might be used to help predict the rate of virus reactivation.